Lecture 1: Cardiovascular & Renal Adaptations in Pregnancy Flashcards
What are adaptations required for in pregnancy?
Increase CO and BV - maintain uteroplacental perfusion and maintain metal demands
How long is human pregnancy (from last menstrual period and fertilisation)?
280 days (40 weeks)
266 days (38 weeks)
What are the physiologic adaptations to pregnancy?
Hyperdynamic, hypermetabolic, hypervolemic, hypercoaguable, low resistance, compensatory respiratory alkalemia, diabetogenic
What is the ideal weight gain in pregnancy and when does it occur?
10-13kg, with 1-2kg in first trimester and 1-2kg/month in the 2nd and 3rd trimesters
Why is there extensive cardiac and resp work during pregnancy?
Additional breast tissue and uterine muscle are major contributors of increase in cardiac and resp work
What is the importance of glucose in pregnancy?
Major energy source for fetal and placental growth
When does maternal hyperglycaemia occur?
Late gestation
Why is there increased insulin synthesis and secretion?
Increased beta cell division and size
How much blood is lost in delivery?
500-600mL vaginal
800-1200mL caeserean
When should blood volume increase?
During pregnancy to accommodate for later loss of blood
What is the % increase of BV and when does it occur?
30-50% - begins at 6 weeks and peaks at 32 weeks
What is the % increase in plasma volume?
40-50%
What is the % increase in red cells mass and when does it occur?
25-30% – begins at 10 weeks and continues until term
Why does red cell mass increase?
Increased erythropoietin and red blood cell production
Why doe physiological anaemia and hemodilution occur?
Increase in blood volume exceeds increase in red blood cells
What is the % increase of white blood cells ad when does it occur?
25-30% - increase in 1st trimester and plateau in 2nd and 3rd
How does the number of total plasma proteins change?
Reduced albumin due to increased blood volume– 1st trimester – changes made contribute to propensity of oedema
What is the % increase of total serum lipids?
40-60%
What is the % of increase in cholesterol and why is this important?
40% - it is an important precursor for oestrogen and progesterone
What are the changes in CV functioning?
Increased CO by 30-50%
- Increased SV from 8 weeks
- Increased HR from 5 weeks
- Increased fluid retention/oedema
What are the changes to BP in pregnancy and when do they occur?
Reduced BP – lowers in 1st trimester and is lowest at 24-32 weeks and returns to normal by term
Is systolic or diastolic BP lower and why?
Diastolic pressure reduced more than systolic due to progesterone and relaxin reducing vascular resistance, blood being directed to placenta and refractory (protective) increases in renin and Ang II
What happens to volume sensors in the kidney during pregnancy?
Reset
What is the % increase of renal blood flow in pregnancy?
40-80%
What is the increase in GFR in pregnancy?
30-50%
How does kidney size change during pregnancy?
Increase by 1m due to increased renal blood flow and glomerular hypertrophy
What does increased renal blood flow and GFR result in?
Increased filtration of water and solutes – increased urine flow and volume. However, renal tubules retain sodium and water to maintain blood/plasma volume expansion
What does blood volume increase to?
7L
When is plasma osmolality reduced?
By week 5 of pregnancy - 10mosmol/kg lower than preconception values by week 10
How does the fluid relate to the foetus function in utero?
Foetus surrounded by fluid - not breathing oxygen, receiving it from mother via placenta. Foetus urinates in utero but don’t want to release toxins into fluid that baby swallows - placenta and mother act as foetal kidneys to filter toxins from womb as kidneys develop. Fluid develops GIT but has no nutritional value - placenta provides nutrition from mother. If these adaptations don’t happen adequately and alter placental function these actions will be compromised
How is oxygen delivered to the baby?
Umbilical vein takes oxygenated blood to baby and umbilical arteries take deoxygenated blood away
How does the placenta avoid problems with vasoconstriction?
Blood lakes
What is the blood flow to the lungs in utero?
Less than 10%
Where is oxygen saturation lowest and highest in the foetus?
Abdominal IVC and umbilical vein
Does the foetus have high or low PO2 and haemoglobin levels?
Low PO2 and high haemoglobin
Why is oxygen consumption higher in foetus?
Lower oxygen saturation but higher oxygen delivery and flow
What are the four shunts for blood in the foetus?
- Ductus Venosus: abdominal umbilical vein to IVC, streamlines blood flow to atria
- Foramen Ovale: right atrium to left atrium
- Dutus Arteriosus: Right ventricle, pulmonary artery to descending aorta, avoid blood perfusion to lungs
- Umbilical circulation – 1 vein brings oxygenation blood from placenta to fetus and 2 arteries remove deoxygenated blood
Why does ductus vernosus close?
Not being used or demanded (probably flow mediated) – closed 1-3 weeks after birth and later in premature babies (trigger unknown)
Why does foramen ovale close?
Pressure change due to airflow when breathing
Why does ductus arteriosus close?
Closes two days after birth due to oxygen mediated inhibition
